A method for one-step preparation of coaxial spiral fibers based on wet spinning

Abstract

The present application relates to the preparation of spiral fibers, in particular to a method for one-step preparation of coaxial spiral fibers based on wet spinning. By microfluidic and coaxial wet spinning method, the coaxial spiral fibers are constructed with polymer / function component as functional core layer and polymer as shell layer. The microflow velocity of different layers is controlled by the coaxial three-hole, and the coaxial spiral fibers with controllable morphology and size, high elongation at break and high sensing sensitivity are obtained by one-step preparation. The process of the present application is simple, and has universality in the field of polymers, and is suitable for large-scale production. The coaxial spiral fibers prepared by the present application have wide application prospects in many fields such as functional clothing, flexible sensing materials and the like.

Description

Technical Field

[0001] The invention relates to the preparation of spiral fibers, and in particular to a one-step preparation method of coaxial spiral fibers based on wet spinning. Background Art

[0002] Nature is home to numerous unique and beautiful structures that contribute to remarkable biological performance. Helical structures are ubiquitous in nature, ranging from DNA, proteins, and polysaccharides at the molecular level, to bacterial flagella and spirulina at the microscopic level, and even to plant tendrils and blood vessels at the macroscopic level. Inspired by these unique helical structures, many researchers have used biomimetic and bioinspired approaches to synthesize devices based on helical fiber structures, which can be used in supercapacitors (Adv Energy Mater 2017, 7, 1600976; Energy Environ Sci 2021, 14, 3075-3085), wearable devices (Angew Chem Int Ed Engl 2021, 60, 25089-25096), and intelligent robots (Adv Mater 2017, 29, 1605765; Nat Commun 2022, 13, 1331), among others. These helical fibers are typically produced by chemical vapor deposition (Carbon 2011, 49, 1101-1107), self-assembly (Am Chem Soc 2020, 142, 19809-19813), electrospinning (Polymer 2020, 201, 122609), wet spinning combined with post-processing (Nat Protoc 2018, 13, 2557-2579), and microfluidic spinning (Angew Chem Int Ed Engl 2017, 56, 12127-12131; Chem Eng J 2022, 447, 137455). For example, active materials were deposited in commercial springs to prepare supercapacitor electrodes with conductivity and high stretchability, but the electrodes produced by this method lacked sufficient wear resistance (Chem Eng J 2018, 349, 168-175). Mingyu Guo et al. (Macromol Rapid Commun 2019, 40, e1900111) proposed a new multifunctional microfluidic spinning strategy for generating helical and superhelical microfibers from hydrophilic (carboxyl chitosan and polyvinyl alcohol), hydrophobic (ethylene-polyvinyl alcohol copolymer), or amphiphilic (linear polyurethane-urea) polymers. In addition, strong polycaprolactone helical microfibers were constructed based on phase reversal microfluidic spinning technology (Angew Chem Int Ed Engl 2021, 60, 25089-25096).Although many excellent works have been successfully carried out to fabricate helical microfibers, only a few polymers (such as alginate 17, chitosan (Macromol Rapid Commun 2019, 40, e1900111), polycaprolactone (Angew Chem Int Ed Engl 2021, 60, 25089-25096) and polyethylene glycol diacrylate (ACS Appl Mater Interfaces 2020, 12, 16097-16103)) have been reported to be able to prepare helical fibers, which greatly limits the development of helical fibers. In addition, the reported helical fibers can be further improved in terms of versatility and durability. A simple and universal method to construct advanced helical fibers is urgently needed to meet this challenge.

[0003] In recent years, due to their unique one-dimensional core-shell structure, coaxial fibers, which include a polymer shell and a functional material core layer, can provide certain protection for the functional material in the core layer, increasing the safety and stability of the core layer material. The resulting conductive coaxial fibers can be widely used in the research of flexible wearable sensors (Adv Mater 2020, 32, e1901806; Adv Mater 2020, 32, e1902301; Adv Mater 2020, 32, e1902532). For example, Joselito M. Razal et al. (Adv Funct Mater 2020, 30, 1910504) used coaxial wet spinning technology to prepare polyurethane / Ti3C2Tx MXene fibers with high elongation (>152%) and conductivity, which can be used as strain sensors. Coaxial wet spinning technology was also used to manufacture fatigue-resistant and highly extensible ion-conductive fibers with a unique coaxial structure, with a thermoplastic elastomer as the outer shell layer and an ionic liquid as the core layer, which can be used to detect human body movement (Compos Commun 2021, 25, 100693). The coaxial wet spinning strategy can also be used to manufacture coaxial fibers with high conductivity and mechanical strength, with graphene oxide / MXene as the conductive core layer and regenerated cellulose as the shell layer (Chem Eng J 2022, 430, 133074). Although the existing literature has made some progress in the optimization and application of the mechanical properties, sensitivity, conductivity, stability and other aspects of coaxial fibers, the focus on the optimization of a single performance and the single shape of the resulting product are difficult to balance with continuous large-scale production, stability, high sensitivity and reusability, which still limits the functionalization of coaxial fibers for smart wearable sensing materials. Summary of the Invention

[0004] The purpose of the present invention is to solve the defects in the prior art and provide a one-step preparation method of coaxial spiral fibers based on wet spinning.

[0005] To achieve the above objectives, the technical solutions provided by the present invention are:

[0006] A one-step preparation method for coaxial helical fibers based on wet spinning. Through microfluidics and coaxial wet spinning, coaxial helical fibers are constructed with polymer / functional components as the functional core layer and polymer as the shell layer. The microflow rate of different layers is controlled by three coaxial holes, and coaxial helical fibers with controllable morphology and size, high elongation at break, and high sensing sensitivity are prepared in one step.

[0007] The diameter of the core layer pinhole of the coaxial three-hole needle is 0.16-0.84 mm, the diameter of the middle layer pinhole is 0.41-1.55 mm, and the diameter of the shell layer pinhole is 0.84-2.27 mm.

[0008] The specific preparation is

[0009] 1) preparing a solution of a polymer substance with a concentration of 5 wt% to 80 wt% as a shell solution of the coaxial helical fiber;

[0010] 2) preparing a coagulation bath solution with a concentration of 10 wt% to 100 wt% as an intermediate layer solution of the coaxial helical fiber;

[0011] 3) preparing a mixed solution containing a polymer substance and a functional component as a core layer solution of the coaxial helical fiber, wherein the concentration of the functional component in the core layer solution is 2% to 90% of the total mass of the polymer substance and the functional component;

[0012] 4) The solutions in 1), 2) and 3) are poured into three separate spinning tanks, respectively, and connected to the shell layer, middle layer and core layer of the three-hole coaxial needle through pipes, respectively. They are controlled by three independent injection pumps and injected into the coagulation tank at the same time, and then stretched and dried to obtain the coaxial spiral fiber.

[0013] The polymer substances in steps 1) and 3) may be the same or different and may be selected from thermoplastic elastomers;

[0014] The functional component is one or more of disulfide, graphene, carbon nanotube, nanosilver, nanogold, MXene and ionic liquid;

[0015] The solution for dissolving the polymer in step 1) is one or more of N,N-dimethylformamide, toluene, ethyl acetate, n-hexane, cyclohexane, and tetrahydrofuran;

[0016] The solution for dissolving the polymer substance and the functional component in step 3) is one or more of N,N-dimethylformamide, toluene, ethyl acetate, n-hexane, cyclohexane, and tetrahydrofuran; wherein the mass ratio of the polymer substance to the functional component is in the range of 49:1 to 1:9.

[0017] The thermoplastic elastomer is styrene-based thermoplastic elastomer (SEBS), thermoplastic polyurethane (TPU), thermoplastic polyolefin elastomer (TPO), polyester elastomer (TPEE); the ionic liquid is a fluorine-containing ionic liquid (such as: 1-hexyl imidazolium trifluoroacetate, 1-octylimidazole tetrafluoroborate, 1-octylimidazole trifluoromethanesulfonate, 1-octylimidazole trifluoroacetate, 1-allyl-3-methylimidazolium hexafluorophosphate, 1-allyl-3-methylimidazolium bistrifluoromethanesulfonyl imide);

[0018] The coagulation bath is one or more of ethanol, methanol, isopropanol, saline solution, and water;

[0019] In the step (4), the coagulation bath in the coagulation tank is consistent with the intermediate layer solution.

[0020] In the step (4), the flow rate of the shell layer solution is 0.1 mL / h to 1000 mL / h, the flow rate of the intermediate layer solution is 0.1 mL / h to 1000 mL / h, and the flow rate of the core layer solution is 0.1 mL / h to 1000 mL / h.

[0021] The invention discloses a coaxial helical fiber based on wet spinning. The coaxial helical fiber with an internal helical distance of 0.01 mm to 10 mm is prepared according to the method.

[0022] Compared with the prior art, the one-step preparation method of coaxial spiral fibers based on wet spinning provided by the present invention has the following advantages:

[0023] The present invention utilizes coaxial wet spinning technology to construct coaxial helical fibers with polymer / functional components as the functional core layer and polymer as the shell layer. By changing the flow rate of the shell layer, intermediate layer, and core layer solutions, coaxial helical fibers with controllable morphology and size, high elongation at break, and high sensing sensitivity are further obtained. Specifically:

[0024] 1) The present invention adopts coaxial wet spinning technology to prepare coaxial spiral fibers in one step, which is applicable to the preparation of coaxial spiral fibers based on various polymers. The operation is simple and easy to control, the morphology and size can be precisely controlled, and the performance is excellent.

[0025] 2) The solvent and coagulation bath components used in the present invention are recyclable, and the recycling technology is mature and reliable. The coaxial helical fibers prepared by the present invention contain composite functional components, which not only have extremely high elongation at break and high sensor sensitivity, but also can simultaneously possess tensile and pressure sensing functions. The entire process is simple, convenient, safe, environmentally friendly, low-cost, and low-investment. The coaxial helical fibers prepared by the present invention have broad application prospects in various fields, such as functional clothing and flexible sensing materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the preparation of coaxial helical fibers and actual photos of the obtained coaxial helical fibers provided in an embodiment of the present invention, wherein (A) is a schematic diagram of the preparation of coaxial helical fibers, and (B) is an actual photo of the coaxial helical fibers. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further illustrated below in conjunction with specific embodiments, which should not be understood as limiting the scope of protection of the present invention. Those skilled in the art may make some non-essential changes and adjustments based on the contents of the above invention, which all fall within the scope of protection of the present invention.

[0028] The one-step preparation method of the coaxial spiral fiber of the present invention cleverly combines microfluidics technology with coaxial wet spinning to prepare coaxial spiral fibers with a controllable internal spiral fiber structure and a cylindrical shell structure. Specifically, a three-hole coaxial microfluidic system with continuous rotation and spiral functions inside the coaxial microfiber is used to scalably generate the required coaxial spiral microfibers by introducing a coagulation layer between the shell layer and the core layer and adjusting the flow rate through the coaxial pinhole for precise regulation. The diameter, length and spiral pitch of the obtained coaxial spiral microfibers are all highly controllable. The prepared coaxial spiral fibers have high elongation at break and high sensing sensitivity, and can be used not only as a tensile sensor, but also as a pressure sensor for detecting human body movement.

[0029] The mechanical properties of the coaxial helical fibers in the following examples were tested using a universal materials testing machine (CMT6503, MTS) in accordance with GB / T 1040.3-2006. The maximum sensitivity of the coaxial helical fiber sensor was calculated using the following formula: GF = (ΔR / R) / ε, where GF is the maximum sensitivity coefficient, ΔR is the difference between the initial and post-stretch resistance, R is the initial resistance, and ε is the elongation.

[0030] Example 1:

[0031] according to Figure 1As shown, 10g of SEBS was added to 10g of ethyl acetate / n-hexane (1:1 by mass) to completely dissolve, yielding a 50wt% SEBS solution (shell layer). Anhydrous ethanol was used for the intermediate layer. 1g of carbon nanotubes was added to 10g of ethyl acetate / n-hexane (1:1 by mass) and ultrasonically mixed until uniformly dissolved. Then, 3g of SEBS was added and stirred to dissolve and mix uniformly, yielding a 3:1 SEBS / CNTs mixed solution (core layer). The syringe pump speed was controlled to achieve flow rates of 15, 31.95, and 5.65mL / h for the shell, intermediate, and core layers, respectively. Wet spinning was performed using anhydrous ethanol as the coagulation bath and coaxial three-hole needles of 20G, 16G, and 13G. After collection and drying, the resulting fibers had a cylindrical shell and a helical core (5.8mm pitch). The coaxial helical fibers had a diameter of 2mm. The breaking strength is 1.4 MPa, the elongation at break is 1100%, and the maximum sensitivity coefficient is 4000. The coagulation bath used is ethanol. After spinning, ethyl acetate / n-hexane can be separated by extraction, and then ethanol can be separated by distillation.

[0032] Example 2:

[0033] 10g of SEBS was added to 10g of ethyl acetate / n-hexane (1:1 by mass) to completely dissolve, yielding a 50wt% SEBS solution (shell layer). Ethanol was used for the intermediate layer. 1g of carbon nanotubes was added to the 1:1 by mass ethyl acetate / n-hexane solution and ultrasonically mixed until uniformly dissolved. 3g of SEBS was then added and stirred to dissolve and mix thoroughly, yielding a 3:1 SEBS / CNTs mixed solution (core layer). Wet spinning was performed using anhydrous ethanol as the coagulation bath, using coaxial three-hole needles of 20G, 16G, and 13G. After collection and drying, the resulting fibers had a cylindrical shell and a helical core (2.5mm pitch). The fibers exhibited a breaking strength of 1.7MPa, an elongation at break of 900%, and a maximum sensitivity coefficient of 2500. The coagulation bath used is ethanol. After spinning, ethyl acetate / n-hexane can be separated by extraction, and then ethanol can be separated by distillation.

[0034] Example 3:

[0035] 10g of SEBS was added to 10g of ethyl acetate / n-hexane (1:1 by mass) to completely dissolve, yielding a 50wt% SEBS solution (shell layer). Ethanol was used for the intermediate layer. 1g of carbon nanotubes was added to the 1:1 by mass ethyl acetate / n-hexane solution and ultrasonically mixed until uniformly dissolved. 3g of SEBS was then added and stirred to dissolve and mix thoroughly, yielding a 3:1 SEBS / CNTs mixed solution (core layer). Wet spinning was performed using anhydrous ethanol as the coagulation bath, using coaxial three-hole needles of 20G, 16G, and 13G. After collection and drying, the resulting fibers had a cylindrical shell and a helical core (1.45mm pitch). The fibers had a breaking strength of 2.0 MPa, an elongation at break of 800%, and a maximum sensitivity coefficient of 1500. The coagulation bath used is ethanol. After spinning, ethyl acetate / n-hexane can be separated by extraction, and then ethanol can be separated by distillation.

[0036] Example 4:

[0037] 10g of SEBS was added to 10g of ethyl acetate / n-hexane (1:1 by mass) to completely dissolve, yielding a 50wt% SEBS solution (shell layer). Ethanol was used for the intermediate layer. 1g of carbon nanotubes was added to the 1:1 by mass ethyl acetate / n-hexane solution and ultrasonically mixed until uniformly dissolved. 3g of SEBS was then added and stirred to dissolve and mix thoroughly, yielding a 3:1 SEBS / CNTs mixed solution (core layer). Wet spinning was performed using anhydrous ethanol as the coagulation bath, using coaxial three-hole needles of 20G, 16G, and 13G. After collection and drying, the resulting fibers had a cylindrical shell and a helical core (pitch 0.26mm). The fibers exhibited a breaking strength of 4.5MPa, an elongation at break of 650%, and a maximum sensitivity coefficient of 620.

[0038] Example 5:

[0039] 10g of SEBS was added to 10g of ethyl acetate / n-hexane (1:1 by weight) to completely dissolve, yielding a 50wt% SEBS solution (shell layer). Ethanol was used for the intermediate layer. 1g of carbon nanotubes was added to the 1:1 by weight ethyl acetate / n-hexane solution and ultrasonically mixed until uniformly dissolved. 3g of SEBS was then added and stirred to dissolve and mix thoroughly, yielding a 3:1 SEBS / CNTs mixed solution (core layer). The syringe pump speed was controlled to achieve flow rates of 15, 30.1, and 7.5mL / h for the shell, intermediate, and core layers, respectively. Wet spinning was performed using a 50wt% ethanol solution as the coagulation bath. Coaxial three-hole needles were used, with 20G, 16G, and 13G tips. After collection and drying, the resulting fibers had a cylindrical shell and a helical core (2.5mm pitch). The fibers had a diameter of 2mm and exhibited a breaking strength of 1.3MPa, an elongation at break of 600%, and a maximum sensitivity coefficient of 3000. The coagulation bath used is ethanol. After spinning, ethyl acetate / n-hexane can be separated by extraction, and then ethanol can be separated by distillation.

[0040] Example 6:

[0041] 10g of SEBS was added to 10g of ethyl acetate / n-hexane (1:1 by weight) to completely dissolve, yielding a 50wt% SEBS solution (shell layer). Ethanol was used for the intermediate layer. 1g of carbon nanotubes was added to the 1:1 by weight ethyl acetate / n-hexane solution and ultrasonically mixed until uniformly dissolved. 3g of SEBS was then added and stirred to dissolve and mix thoroughly, yielding a 3:1 SEBS / CNTs mixed solution (core layer). The syringe pump speed was controlled to achieve flow rates of 15, 30.1, and 7.5mL / h for the shell, intermediate, and core layers, respectively. Wet spinning was performed using a 25wt% ethanol solution as the coagulation bath. Coaxial three-hole needles were used, with 20G, 16G, and 13G tips. After collection and drying, the resulting fibers had a cylindrical shell and a helical core (2.5mm pitch). The fibers had a diameter of 2mm. The fibers exhibited a breaking strength of 1.1MPa, an elongation at break of 450%, and a maximum sensitivity coefficient of 3500. The coagulation bath used is ethanol. After spinning, ethyl acetate / n-hexane can be separated by extraction, and then ethanol can be separated by distillation.

[0042] Example 7:

[0043] 5.5g of polyurethane was added to 4.5g of N,N-dimethylformamide (DMF) and completely dissolved to obtain a 55wt% polyurethane solution (shell layer). Ethanol was used as the intermediate layer. 1g of graphene oxide was added to the DMF and ultrasonically mixed until uniformly dissolved. Then, 4g of polyurethane was added and stirred to dissolve and mix uniformly, resulting in a polyurethane / graphene oxide mixed solution with a mass ratio of 4:1 (core layer). The syringe pump speed was controlled to achieve flow rates of 15, 22.6, and 15 mL / h for the shell, intermediate, and core layers, respectively. Wet spinning was performed using anhydrous ethanol as the coagulation bath and coaxial three-hole needles of 20G, 16G, and 13G gauge. After collection and drying, the resulting fibers had a cylindrical shell and a helical core (pitch 0.51mm). The fibers had a diameter of 2.2mm and exhibited a breaking strength of 1.3 MPa and an elongation of 600%. The coagulation bath used is ethanol. After the spinning is completed, ethanol has a low boiling point and DMF has a high boiling point, so ethanol and DMF can be separated by distillation.

[0044] Example 8:

[0045] 5.5g of polyurethane was added to 4.5g of N,N-dimethylformamide (DMF) and completely dissolved to obtain a 55wt% polyurethane solution (shell layer). Ethanol was used as the intermediate layer. 1g of graphene oxide was added to the DMF and ultrasonically mixed until uniformly dissolved. Then, 4g of polyurethane was added and stirred to dissolve and mix uniformly, resulting in a polyurethane / graphene oxide mixed solution (core layer) with a mass ratio of 4:1. The syringe pump speed was controlled to achieve flow rates of 15, 17.6, and 20 mL / h for the shell, intermediate, and core layers, respectively. Wet spinning was performed using anhydrous ethanol as the coagulation bath and coaxial three-hole needles of 20G, 16G, and 13G gauge. After collection and drying, the resulting fibers had a cylindrical shell and a helical core (pitch 0.26mm). The fibers had a diameter of 2.2mm and exhibited a breaking strength of 1.5 MPa and an elongation of 500%. The coagulation bath used is ethanol. After the spinning is completed, ethanol has a low boiling point and DMF has a high boiling point, so ethanol and DMF can be separated by distillation.

[0046] Example 9:

[0047] 5.5g of polyurethane was added to 4.5g of N,N-dimethylformamide (DMF) and completely dissolved to obtain a 55wt% polyurethane solution (shell layer). Ethanol was used as the intermediate layer. 1g of graphene oxide was added to the DMF and ultrasonically mixed until uniformly dissolved. Then, 4g of polyurethane was added and stirred to dissolve and mix uniformly, resulting in a polyurethane / graphene oxide mixed solution with a mass ratio of 4:1 (core layer). Wet spinning was performed by controlling the syringe pump speed to achieve flow rates of 15, 90, and 110 mL / h for the shell, intermediate, and core layers, respectively. Deionized water was used as the coagulation bath, and coaxial three-hole needles were used, with 20G, 16G, and 13G gauges. After collection and drying, the resulting fibers had a cylindrical shell and a helical core (pitch 0.24mm). The fibers had a diameter of 4mm and exhibited a breaking strength of 1.7 MPa and an elongation of 450%.

[0048] Example 10:

[0049] 5.5g of polyurethane was added to 4.5g of N,N-dimethylformamide (DMF) and completely dissolved to obtain a 55wt% polyurethane solution (shell layer). Ethanol was used as the intermediate layer. 1g of gold nanoparticles was added to the DMF and ultrasonically mixed until uniformly dissolved. Then, 4g of polyurethane was added and stirred to dissolve and mix uniformly, resulting in a polyurethane / gold nanoparticle mixed solution (core layer) with a mass ratio of 4:1. The syringe pump speed was controlled to achieve flow rates of 15, 100, and 200mL / h for the shell, intermediate, and core layers, respectively. Wet spinning was performed using a coagulation bath of 50wt% ethanol and coaxial three-hole needles of 20G, 16G, and 13G gauge. After collection and drying, the resulting fibers had a cylindrical shell and a helical core (pitch 0.15mm). The coaxial helical fibers had a diameter of 5mm. The fibers exhibited a breaking strength of 1.4MPa and an elongation at break of 350%.

[0050] Example 11:

[0051] 5.5g of polyurethane was added to 4.5g of N,N-dimethylformamide (DMF) and completely dissolved to obtain a 55wt% polyurethane solution (shell layer). Isopropyl alcohol was used as the intermediate layer. 1g of silver nanoparticles was added to the DMF and ultrasonically mixed until uniformly dissolved. Then, 4g of polyurethane was added and stirred to dissolve and mix uniformly, resulting in a polyurethane / silver nanoparticle mixed solution (core layer) with a mass ratio of 4:1. The syringe pump speed was controlled to achieve flow rates of 15, 150, and 110 mL / h for the shell, intermediate, and core layers, respectively. Wet spinning was performed using a 95wt% isopropyl alcohol coagulation bath and coaxial three-hole needles with 20G, 16G, and 13G gauges. After collection and drying, the resulting fibers had a cylindrical shell and a helical core (pitch 0.41mm). The fibers had a diameter of 4.5mm and exhibited a breaking strength of 1.2MPa and an elongation at break of 500%. The coagulation bath used is isopropyl alcohol. After spinning, isopropyl alcohol has a low boiling point and DMF has a high boiling point, so isopropyl alcohol and DMF can be separated by distillation.

[0052] Example 12:

[0053] 5.5g of polyurethane was added to 4.5g of N,N-dimethylformamide (DMF) and completely dissolved to obtain a 55wt% polyurethane solution (shell layer). Isopropyl alcohol was used as the intermediate layer. 1g of silver nanoparticles was added to the DMF and ultrasonically mixed until uniformly dissolved. Then, 4g of polyurethane was added and stirred to dissolve and mix uniformly, resulting in a polyurethane / silver nanoparticle mixed solution (core layer) with a mass ratio of 4:1. The syringe pump speed was controlled so that the flow rates for the shell, intermediate layer, and core layer were 15, 100, and 160mL / h, respectively. Wet spinning was performed using a 100wt% isopropyl alcohol coagulation bath and coaxial three-hole needles with 24G / 16G / 13G gauges. After collection and drying, the resulting fibers had a cylindrical shell and a helical core (pitch 0.19mm). The fibers had a diameter of 4.5mm. The fibers exhibited a breaking strength of 1.4MPa and an elongation at break of 400%. The coagulation bath used is isopropyl alcohol. After spinning, isopropyl alcohol has a low boiling point and DMF has a high boiling point, so isopropyl alcohol and DMF can be separated by distillation.

[0054] Example 13:

[0055] 5.5g of polyurethane was added to 4.5g of N,N-dimethylformamide (DMF) and completely dissolved to obtain a 55wt% polyurethane solution (shell layer). Methanol was used as the intermediate layer. 1g of silver nanoparticles was added to the DMF and ultrasonically mixed until uniformly dissolved. Then, 4g of polyurethane was added and stirred to dissolve and mix uniformly, resulting in a polyurethane / silver nanoparticle mixed solution (core layer) with a mass ratio of 4:1. The syringe pump speed was controlled to achieve flow rates of 15, 50, and 50 mL / h for the shell, intermediate, and core layers, respectively. Wet spinning was performed using anhydrous methanol as the coagulation bath and coaxial three-hole needles of 24G, 16G, and 13G gauge. After collection and drying, the resulting fibers had a cylindrical shell and a helical core (pitch 0.3mm). The fibers had a diameter of 3mm. The fibers exhibited a breaking strength of 1.6MPa and an elongation at break of 350%. The coagulation bath used is methanol. After the spinning is completed, methanol has a low boiling point and DMF has a high boiling point, so methanol and DMF can be separated by distillation.

[0056] Example 14:

[0057] 5.5 g of polyester elastomer (TPEE) was added to 4.5 g of toluene to completely dissolve it, yielding a 55 wt% TPEE solution (shell layer). Ethanol was used as the intermediate layer. 0.2 g of 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt was added to the toluene and ultrasonically mixed until uniformly dissolved. 4 g of TPEE was then added and stirred to dissolve and mix uniformly, yielding a TPEE / 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt mixed solution (core layer) with a mass ratio of 4:0.2. The syringe pump speed was controlled to achieve flow rates of 30, 50, and 150 mL / h for the shell, intermediate, and core layers, respectively. Wet spinning was performed using anhydrous ethanol as the coagulation bath and coaxial three-hole needles with 26G, 16G, and 12G gauges. After collection and drying, the resulting fibers had a cylindrical shell and a helical core (0.2 mm pitch). The coaxial helical fibers had a diameter of 5 mm. The breaking strength is 1.3 MPa and the breaking elongation is 700%. The coagulation bath used is ethanol. After the spinning is completed, the toluene can be separated by extraction and then the ethanol can be separated by distillation.

[0058] Example 15:

[0059] 5.5g of thermoplastic polyolefin elastomer (TPO) was added to 4.5g of ethyl acetate / cyclohexane to completely dissolve to obtain a 55wt% polyurethane solution (shell layer); ethanol was used as the intermediate layer; 0.2g of 1-octylimidazole trifluoroacetate was added to the ethyl acetate / cyclohexane solution and ultrasonically mixed until uniformly dissolved; then 4g of TPEE was added and stirred to dissolve and mix uniformly to obtain a TPO / 1-octylimidazole trifluoroacetate mixed solution (core layer) with a mass ratio of 4:0.2. The speed of the syringe pump was controlled so that the flow rates of the shell, intermediate layer, and core layer were 30, 50, and 150 mL / h, respectively. Wet spinning was performed in anhydrous ethanol as the coagulation bath, using a coaxial three-hole needle with a model of 26G / 16G / 12G. After collection and drying, a stretchable coaxial helical fiber with a cylindrical shell layer and a helical core layer (pitch of 0.2mm) was obtained. The coaxial helical fiber had a diameter of 5mm. The breaking strength is 1.1 MPa and the breaking elongation is 1000%. The coagulation bath used is ethanol. After spinning, the ethyl acetate / cyclohexane can be separated by extraction, and then the ethanol can be separated by distillation.

Claims

1. A one-step method for preparing coaxial spiral fibers based on wet spinning, characterized in that: Through microfluidics and coaxial wet spinning, coaxial helical fibers are constructed with polymer / functional components as the functional core layer and polymer as the shell layer. The microfluidic flow rate of different layers is controlled by three coaxial holes, and coaxial helical fibers with controllable morphology and size, high elongation at break, and high sensing sensitivity are prepared in one step. 1) preparing a solution of a polymer substance with a concentration of 5 wt% to 80 wt% as the shell solution of the coaxial helical fiber; 2) preparing a coagulation bath solution with a concentration of 10 wt% to 100 wt% as an intermediate layer solution of the coaxial helical fiber; 3) preparing a mixed solution containing a polymer substance and a functional component as the core layer solution of the coaxial helical fiber, wherein the concentration of the functional component in the core layer solution is 2% to 90% of the total mass of the polymer substance and the functional component; 4) The solutions in 1), 2) and 3) are poured into three separate spinning tanks, respectively, and connected to the shell layer, middle layer and core layer of a three-hole coaxial needle through pipes. They are controlled by three independent injection pumps and injected into a coagulation tank at the same time. The coaxial spiral fibers are then stretched and dried to obtain the coaxial spiral fibers.

2. The one-step preparation method of coaxial spiral fibers based on wet spinning according to claim 1, characterized in that: The diameter of the core layer pinhole of the coaxial three-hole needle is 0.16-0.84 mm, the diameter of the middle layer pinhole is 0.41-1.55 mm, and the diameter of the shell layer pinhole is 0.84-2.27 mm.

3. The one-step preparation method of coaxial spiral fibers based on wet spinning according to claim 1, characterized in that: The high molecular weight substances in steps 1) and 3) may be the same or different and may be selected from thermoplastic elastomers; The functional component is one or more of disulfide, graphene, carbon nanotube, nanosilver, nanogold, MXene and ionic liquid; The solution for dissolving the polymer in step 1) is one or more of N,N-dimethylformamide, toluene, ethyl acetate, n-hexane, cyclohexane, and tetrahydrofuran; In step 3), the solution for dissolving the polymer substance and the functional component is one or more of N,N-dimethylformamide, toluene, ethyl acetate, n-hexane, cyclohexane, and tetrahydrofuran; wherein the mass ratio of the polymer substance to the functional component is in the range of 49:1 to 1:

9.

4. The one-step preparation method of coaxial helical fibers based on wet spinning according to claim 3, characterized in that: The thermoplastic elastomer is styrene-based thermoplastic elastomer (SEBS), thermoplastic polyurethane (TPU), thermoplastic polyolefin elastomer (TPO), or polyester elastomer (TPEE); the ionic liquid is a fluorine-containing ionic liquid; and the coagulation bath is one or more of ethanol, methanol, isopropanol, and salt solution.

5. The one-step preparation method of coaxial spiral fibers based on wet spinning according to claim 3, characterized in that: The coagulation bath in the coagulation tank in step (4) is kept consistent with the intermediate layer solution.

6. The one-step preparation method of coaxial spiral fibers based on wet spinning according to claim 1, characterized in that: In step (4), the flow rate of the shell layer solution is 0.1 mL / h to 1000 mL / h, the flow rate of the intermediate layer solution is 0.1 mL / h to 1000 mL / h, and the flow rate of the core layer solution is 0.1 mL / h to 1000 mL / h.

7. A coaxial helical fiber prepared by the method of claim 1 based on wet spinning, characterized in that: Coaxial helical fibers with an internal helical distance of 0.01 mm to 10 mm are prepared according to the method of claim 1.

Images